Buteo lagopus

Buteo lagopus

The rough-legged buzzard or rough-legged hawk (Buteo lagopus Pontoppidan, 1763) is a bird of prey belonging to the Accipitridae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Phylum Chordata,
Aves class,
Order Accipitriformes,
Family Accipitridae,
Genus Buteo,
Species B. lagopus.
The terms are synonyms:
– Archibuteo lagopus (Pontoppidan, 1763);
– Falco lagopus Pontoppidan, 1763;
– Falco spec Pontoppidan, 1763.
Within this species, the following subspecies are recognised:
– Buteo lagopus subsp. kamtschatkensis Dementiev, 1931; this subspecies breeds from northern Siberia to the Pacific of North America. It has paler plumage than the B. l. sanctijohannis and is, on average, the largest of the three subspecies.
– Buteo lagopus subsp. lagopus; it is the nominate subspecies which breeds in northern Europe and Asia and has a relatively dark plumage. The dorsal feathers are a homogeneous brown colour, which contrasts well with the paler head.
– Buteo lagopus subsp. menzbieri Dementiev, 1951; it is a subspecies with fragmented ranges, with presences in the center of the Asian continent, China and northern Japan.
– Buteo lagopus subsp. sanctijohannis (Gmelin, 1788); this subspecies nests in North America. It has a pale, speckled dorsal plumage and is slightly smaller than the B. l. lagopus.

Geographic Distribution and Habitat –
The Buteo lagopus is a bird of prey that lives in the northernmost areas of Europe, North America and Asia.
Its breeding occurs in the tundra and taiga habitats of North America and Eurasia between latitudes 61° and 76°N. These birds are found in North America and migrate to southern Canada and the central United States for the winter, while Eurasian individuals migrate to southern Europe and Asia. It is the only member of its genus that is found on both northern continents and has a complete circumpolar distribution. During these winter months, November through March, preferred habitats include marshes, grasslands, and agricultural regions where rodent prey is most abundant.
It is an erratic bird of prey that can also be accidentally seen in Italy.
Its most frequent breeding habitat is in areas with an abundance of open, non-forested land. Depending on the snow conditions, the migrants arrive at the breeding grounds in April and May.

Description –
The Buteo lagopus is a medium-large sized bird of prey.
It has a length of 46-68 cm, with a wingspan ranging from 120 to 153 cm. Individuals can weigh from 600 to 1,660 g, with females typically being larger and heavier than males. Weight appears to increase from summer to winter in adults, ranging from an average of 822 to 1,027 g in males and from 1,080 to 1,278 g in females.
Among standard measurements in adults, the chord is 37.2–48.3 cm, the tail is 18.6–25.5 cm, the tip is 3.2–4.5 cm, and the tarsus is 5.8–7.8cm.
The plumage is predominantly brown in color and often displays a high degree of mottling.
There is a broad brown breast band in most plumages, and a dark square carpal patch contrasting with the white under the wing is an easily identifiable feature in light morph individuals.
It has a wide variety of plumage patterns, light and dark, from males to females and adults to juveniles. Extensive field experience is required to distinguish between some plumage variations.
The juveniles have dorsal feathers with more extensive pale edges, and a pale bib with larger spots than in the adults.
Compared to its more common Nearctic and Palearctic cousins, the common buzzard (Buteo buteo) and the red-tailed hawk (Buteo jamaicensis), it is slightly larger, although it may be surpassed by the latter.
Its feet are feathered to the toes as an adaptation to its arctic home range.
Distinctive features in all plumages include long white tail feathers with one or more dark subterminal bands. The wing tips are long enough to reach or extend beyond the tail when the animal is perched.
The common buzzard can be similar in appearance, with a similar long-tailed shape, and can be notoriously variable in plumage.
B. lagopus has longer wings and looks more like an eagle.
Adults make alarm calls when intruders approach a nesting site. this vocalization is described as a low-pitched, low-pitched whistle, sounding like kiu wiyuk or a long descending kee-eer.
This cry is emitted in flight or from a perch every 15-30 seconds. During courtship, both sexes emit a whistling sound that turns into a hissing sound. After copulation, females will make a clucking sound and males will vocalize a whistling sound.
The chicks emit small sounds related to the request for food.

Biology –
Buteo lagopus reaches sexual maturity at around two years of age.
The reproduction generally takes place in the month of May, but it varies according to the dates of arrival in the breeding places. It is thought to be monogamous, mating with a single individual for multiple years. No evidence currently suggests otherwise.
These birds of prey are looking for a suitable nesting area not in spring, like most migratory birds, but in early autumn. After the breeding season, they make long-distance prospecting flights, look for suitable habitat with large numbers of rodents, and return to that location the following year.
Nests are built soon after arrival at breeding grounds and take 3-4 weeks to complete. They are made from various materials such as twigs, sedges and old feathers.
The nests have a diameter of 60–90 cm and a height of 25–60 cm.
Preferred nesting sites are rock ledges and rocky outcrops.
Females can lay 1 to 7 eggs, but typically lay 3-5. The average egg size is 56.4 mm long by 44.7 mm wide.
The incubation period is 31 days, provided almost exclusively by the female. The male feeds the female during this incubation period. After hatching, the chicks require 4-6 weeks before fledging in the nest. The chicks depend on the parents for food for 2-4 weeks after leaving the nest.
These birds of prey can nest in association with the Falco peregrinus.
The B. lagopus that survive to adulthood can live up to 19 years in the wild. In captivity, their life span is considerably longer. However, in nature, perhaps the majority of individuals do not survive beyond the first two years of life. Threats faced by juveniles can include starvation when prey is small, freezing when northern climates are particularly harsh during brooding, destruction by humans, and predation by various animals. The chances of survival increase incrementally both when they reach the fledging stage and when they can start hunting on their own. The deaths of flying immatures and adults are often the result of human activities, including collisions with power lines, buildings and vehicles, accidental ingestion of poison or lead from prey items, or illegal hunting and trapping.

Ecological role –
The scientific name of this bird of prey reflects its characteristics; the generic name Buteo is the Latin name of the common buzzard, and lagopus, comes from the ancient Greek lago (λαγως), which means “hare”, and pous (πους), “foot”. Its claws are relatively small, reflecting their favorite prey items.
It is a carnivorous bird that typically feeds on small mammals, which make up 62-98% of its diet. Lemmings and water voles are the main prey items for this species, seasonally constituting up to 80-90% of their prey items, but this varies according to seasonal availability. Some evidence suggests that these hawks may be able to see vole scent marks that are only visible in the ultraviolet range, allowing them to locate prey. While generally preying on rodents, a 2015 paper reported that the species breeds on rodent-free Kolguev Island in Arctic Russia with goslings as its primary prey. In northwestern Russia, these falcons may feed on small rodents in years when rodent densities are high and move for alternative prey (ptarmigan and hares) in years when small rodents are scarce. It supplements its diet with mice, rats, gerbils, pikas, shrews, squirrels of the genera Spermophilus and Tamias, and insects. Besides mammals, birds are the second favorite type of prey for these falcons. Most avian prey species are small passerines such as Plectrophenax nivalis, Calcarius lapponicus and Spizelloides arborea. However, they will also prey on birds slightly larger than the typically targeted passerines, particularly rock ptarmigan (Lagopus ssp.), as well as waterfowl, shorebirds, such as Philomachus pugnax and Asius flammeus. They typically target prey from birds that are young and inexperienced, with relatively large avian prey items often being caught in their fledging stage.
When small mammals are scarce, the Buteo lagopus also nourishes of larger and medium-sized mammals including Cynomys ssp., Ondatra zibethicus, Mustela ssp. and large animals such as Lepus californicus.
During winter, shrub-steppe habitats appear to encourage a heavy reliance on rabbit prey. In developed areas of England, wintering buzzards have been recorded more regularly preying on relatively large prey items such as wood pigeon (Columba palumbus) and invasive European rabbits (Oryctolagus cuniculus).
The Buteo lagopus hunts opportunistically, occasionally supplementing its diet with carrion but mainly focusing on the more locally abundant small vertebrates.
These falcons will also steal prey from other individuals of the same species as well as other species such as Buteo jamaicensis, Circus cyaenus, Falco sparverius and Corvus corax.
Prey sizes typically range from 6.5 to 2,587 g, and adults require 80 to 120 g of food per day.
These birds of prey hunt during the day. Like most Buteos, these hawks have been reported both still hunting (viewing prey from a perch and then ducking) and observing prey in flight. Unlike most other large birds of prey, they can engage in hovering flights above the ground while searching for prey.
As for their predators, the Buteo lagopus is mainly preyed upon when the young are still in the nest.
Arctic foxes (Vulpes lagopus), brown bears (Ursus arctos) and wolverines (Gulo gulo) feed on eggs.
Also other birds such as Stercorarius ssp. and Bubo scandiacus are potential nest predators.
The adults, being large birds of prey, have fewer natural predators but may die in conflicts, especially if they are defending their nests and are occasionally preyed upon by other large birds of prey. Birds of prey that prey on these hawks may include numerous eagles (particularly golden eagles (Aquila chrysaetos), although sometimes other eagles in Eurasia and rarely Haliaeetus eagles as well as large hawks. While wintering they may be vulnerable to nocturnal predation by the Eurasian eagle owl (Bubo bubo) or the great horned owl (Bubo virginianus) and rarely, during the day, other large Buteo falcons, including those of their own species.
In addition to predation, other environmental factors and particular events can also affect nestlings above all.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– C.Battisti, D. Taffon, F. Giucca, 2008. Atlas of nesting birds, Gangemi Editore, Rome.
– L. Svensson, K.Mullarney, D. Zetterstrom, 1999. Guide to Birds of Europe, North Africa and the Near East, Harper Collins Publisher, UK.

Photo source:
– https://www.artsobservasjoner.no/MediaLibrary/2023/1/a2d91cee-85a2-4fb4-92de-1c04567858b8_image.jpg